β-cyclodextrin-modulated ratiometric supramolecular BODIPY fluoroprobe for highly selective and sensitive detection of thiophenol

Thiophenol (PhSH) is an important industrial intermediate but displays significant toxicity towards environmental and biological systems. Here, we introduce a supramolecular system based on β-cyclodextrin (β-CD) and boron dipyrromethene (BODIPY) as a ratiometric fluorescence probe to discriminate PhSH in environmental water samples, cells, and in vivo. In aqueous solutions, BODIPY shows extremely weak fluorescence intensity due to its aggregation into nanometer-sized clusters, which prevents its interaction with thiols. However, within a β-CD environment, it can selectively and sensitively detect PhSH. Also, the stability of the probe was significantly improved. The mechanism studies based on stoichiometry, NMR spectroscopy, and theoretical calculation revealed distinct intermolecular interactions between β-CD and BODIPY, including host-guest interactions and hydrogen bonds. Low limit of detection (10.7 nM) and rapid response time (5 min) have been achieved, and the practicality of the supramolecular system (BODIPY@β-CD) has been verified by actual sample analysis. Furthermore, the first hydrogel-based sensing system for portable PhSH detection has been developed, facilitating rapid and on-site colorimetric visualization across both liquid and gas phases. Most importantly, using a low amount of the probe, early stages of low-dose exposure to PhSH can be visualized in living cells and zebrafish. Therefore, BODIPY@β-CD is a robust new monitoring tool for the detection of PhSH in various scenarios, indicating the promising application value of the host-guest supramolecular probe in detecting highly toxic substances.

Two red/blue-emitting fluorescent probes for quick, portable, and selective detection of thiophenol in food, soil and plant samples, and their applications in bioimaging

Thiophenol (PhSH), which is widely used in many industries, poses significant health risks owing to its acute toxicity and irritating effects. Thus, the detection of PhSH is crucial for ensuring environmental and food safety. There is significant room for improvement in the sensing properties of the reported analytical methods, such as response time, detection limit, selectivity, and portable detection. Herein, we present two new red/blue fluorescence-emissive sensors (NS1 and NS2) for PhSH detection. After reacting with PhSH, NS1 exhibited a low detection limit (66.7 nM), red emission, fast response time of just 10 s, and large Stokes shift (240 nm). NS2 could detect PhSH with a low detection limit (75.8 nM), fast response time of 20 s, and blue emission. The noticeable color response and portability of the two probes made them suitable for on-site detection of PhSH in various samples, such as water, soil, plant, food samples, and living cells. Moreover, it has been shown that these probes could be used to determine PhSH content in smartphone applications, thin layer chromatography kits, and polysulfone capsule kits. Prepared probes have low cytotoxicity and show good permeability in tested living cells, which is important for early diagnosis, disease research, and emergency analysis. Compared with other studies, the proposed approach has remarkable advantages in terms of detection limit, portability, response time, and low cytotoxicity. Thus, it meets the crucial demand for ensuring health, environmental and food safety, and adherence to regulatory standards.

A spectroscopic probe with FRET-ICT feature for thiophenol monitoring in real water samples

Thiophenol (PhSH) is widely used in industry, however, it is extremely harmful to the environment and human health due to its high toxicity. In this work, we developed a new FRET-ICT-based ratiometric fluorescent and colorimetric probe (DMNP) for detecting PhSH. DMNP had an ultrahigh energy transfer efficiency (99.7%) and clear spacing of two emission peaks (133 nm). DMNP achieved a fast response to PhSH and exhibited drastic enhancement (over 2100 folds) of the fluorescence intensity ratio upon addition of PhSH. DMNP showed good linear response in the PhSH concentration ranges of 0.5-13 μM and 17.0-22.0 μM. Meanwhile, DMNP could also be applied to monitor PhSH in a variety of real water samples.

Novel Formulations Containing Fluorescent Sensors to Improve the Resolution of 3D Prints

Three-dimensional printing in SLA (stereolithography) and DLP (digital light processing) technologies has recently been experiencing a period of extremely rapid development. This is due to the fact that researchers recognise the many advantages of 3D printing, such as the high resolution and speed of the modelling and printing processes. However, there is still a search for new resin formulations dedicated to specific 3D printers allowing for high-resolution prints. Therefore, in the following paper, the effects of dyes such as BODIPY, europium complex, and Coumarin 1 added to light-cured compositions polymerised according to the radical mechanism on the photopolymerisation process speed, polymerisation shrinkage, and the final properties of the printouts were investigated. The kinetics of the photopolymerisation of light-cured materials using real-time FT-IR methods, as well as printouts that tangibly demonstrate the potential application of 3D printing technology in Industry 4.0, were examined. These studies showed that the addition of dyes has an effect on obtaining fluorescent prints with good resolution.

Rational design of a new near-infrared fluorophore and apply to the detection and imaging study of cysteine and thiophenol

The development of a near-infrared fluorophore with excellent fluorescence performance, a large Stokes shift, and good biocompatibility has become a focus in the field of fluorescence imaging in recent years. Based on quantum chemistry calculations and reasonable molecular design strategies, a new NIR fluorophore was developed and characterized by simple synthesis, easy structural modification, and a large Stokes shift (105 nm). Furthermore, two new "activatable" fluorescent probes QN-Cys and QN-DNP were synthesized using a simple structural modification. The probe QN-Cys can recognize Cys with high sensitivity (LOD = 128 nM) and high selectivity, and its fluorescence intensity has a good linear relationship with the Cys concentration in the range of 5-35 μM. Furthermore, probe QN-Cys can effectively distinguish Cys from Hcy and GSH, and was successfully applied to the detection and imaging of Cys in human serum, cells, and zebrafish. The probe QN-DNP showed a good specific and sensitive (LOD = 78 nM) fluorescence response to thiophenol, and its fluorescence intensity has a good linear relationship with the thiophenol concentration in the range of 5-30 μM. Furthermore, it was successfully applied to detect thiophenol in real water samples with good recoveries (97-102%), and image thiophenol in living cells, zebrafish and mice. Notebly, the QN-DNP probe could be applied to visualize the distribution of thiophenol in the mice.

A fluorescent probe based on ICT for selective detection of benzenethiol derivatives

This work presented a benzothiazole-based fluorescent probe for the detection of benzenethiol derivatives using 2, 4-dinitrobenzene moiety as a sensing unit. This probe (NCABT) was able to instantaneously respond to 4-methylbenzenethiol (MTP) within 5 min. In detecting MTP, this probe displayed a low limit of detection (49 nM). Furthermore, the probe has been proved to have the potential to detect benzenethiol derivatives with electron-donating group in real water samples.

Design, synthesis and biological activity of bis-sulfonyl-BODIPY probes for tumor cell imaging

In recent years, BODIPY derivatives have become one of the research hotspots in the field of bioprobes, but most of them have the problems of poor hydrophilicity, low biocompatibility and no targeting. In this paper, novel ethylenediamine bridging bis-sulfonyl-BODIPY fluorescent probes were successfully designed and synthesized to solve these problems; What's more, the cytotoxicity analysis, cell imaging, in vivo imaging and apoptosis experiments were carried out. Ethylenediamine bridges and oxygen-rich sulfonyl groups made such probes had certain hydrophilicity, so they could be dissolved in dimethylsulfoxide and methanol. The IC₅₀ value of compound 9 in HCT-116 cells was 93.12 ± 6.33 µM, and in HeLa cells was 89.09 ± 11.84 µM, which indicating that the probe had certain inhibitory effect on cancer cells. The excellent biocompatibility and potential tumor targeting properties of the compound were clearly observed in cell and mice imaging. This study is of great significance for the rational design of novel targeted BODIPY probes with good hydrophilicity and biocompatibility.

pH/glutathione-responsive release of SO2 induced superoxide radical accumulation for gas therapy of cancer

A pH/glutathione (GSH)-responsive SO₂ generation nanoplatform (BODS NPs) is established to achieve lysosomal escape and GSH depletion in tumors to sensitize the SO₂-mediated oxidative stress.

Recent Progress in the Development of Fluorescent Probes for Thiophenol

Thiophenol (PhSH) belongs to a class of highly reactive and toxic aromatic thiols with widespread applications in the chemical industry for preparing pesticides, polymers, and pharmaceuticals. In this review, we comprehensively summarize recent progress in the development of fluorescent probes for detecting and imaging PhSH. These probes are classified according to recognition moieties and are detailed on the basis of their structures and sensing performances. In addition, prospects for future research are also discussed.

Activity-Based Sensing and Theranostic Probes Based on Photoinduced Electron Transfer

Fluorescent probes have become powerful tools in detection, imaging and disease diagnosis due to their high sensitivity, specificity, fast response, and technical simplicity. In the last decades, researchers have made remarkable progress in developing signaling mechanisms to design fluorescent probes such as photoinduced electron transfer (PET), intramolecular charge transfer (ICT), and fluorescence resonance energy transfer (FRET). Typical PET is composed of a multicomponent system in which a fluorophore (electron acceptor) is separately linked with a recognition group (electron donor) via a short spacer. PET probes normally feature a low fluorescence background and significant fluorescence enhancement in response to targets. Recent research revealed that PET probes have also been used as theranostic agents, whose fluorescence and toxicity can be simultaneously activated by cancer-specific parameters. In this Account, we highlight the recent advances of rational design and applications of PET probes, focusing primarily on studies from our research group. For example, different from the case of the traditional single-atom electron donor (O, S, N, Se, Te, etc.) in typical PET, we used more a electron-rich pyrrole ring to "switch off" the fluorescence of the fluorophore more efficiently through an "enhanced PET" effect which provided a lower background fluorescence and higher signal-to-noise ratio. Furthermore, normal PET represents the main principle behind the design of small molecule "off-on" fluorescent sensors. We developed new PET platform through intramolecular space folding (folding PET) to overcome the difficulty of designing PET enzyme-targeting probes. Therefore, based on typical PET and these new PET concepts, we, for instance, reported PET probes for the detection of Zn²⁺ without proton interference, a BODIPY-based d-PET probe for reporting local hydrophilicity within lysosomes, and an "enhanced PET" fluorescent probe for imaging HClO in cancer cells. We also developed COX-2-specific probe for identifying cancer cells and quantifying cancer-related events, and a KIAA1363-sensitive probe for tracking solid tumors in living mice. Furthermore, we first applied an aminopeptidase N (APN)-sensitive probe based on PET for cancer diagnosis and therapy. We anticipate that further development of PET fluorescent probes providing more sensitivity and selectivity to analytes of interest will be equipped with more functions and play indispensable roles in the studies of pathology, diagnostics, and cancer therapies.

Development of a red-light emission hypoxia-sensitive two-photon fluorescent probe for in vivo nitroreductase imaging

The overexpression of nitroreductase (NTR) in hypoxia has been recognized as a biomarker of highly aggressive disease, and the development of a hypoxia-sensitive two-photon (TP) bioimaging probe with both excitation and emission wavelengths in the red-light region provides favorable deep-tissue imaging with a low background fluorescence signal. Although quite a few TP hypoxia-sensitive fluorescent probes have been reported for NTR detection, their short emission wavelength (<550 nm) limits their application. Herein, we report a red light emissive TP hypoxia-sensitive turn-on probe (NRP) by employing Nile Red as a red-emitting fluorophore and p-nitrobenzene as an NTR recognition group with improved sensitivity. The NRP probe showed obvious strong red-fluorescence enhancement in the presence of NTR and high selectivity toward NTR in aqueous solution. Our in vitro experimental results illustrated that the NRP loaded tumor cells treated under hypoxia display remarkably strong fluorescence in both OP and TP microscopy at 655 nm with 45-fold enhancement, which affords deep-tissue penetration ability. The NRP probe was also successfully applied for imaging NTR in liver tissue slices and a 4T1-bearing mice model, which is important for bioimaging applications.

Celecoxib Conjugated Fluorescent Probe for Identification and Discrimination of Cyclooxygenase-2 Enzyme in Cancer Cells

Cyclooxygenase-2 (COX-2) is an enzyme overexpressed in most types of cancers and has been used for an excellent targetable biomarker. Celecoxib is an effective inhibitor of COX-2, used in anti-inflammation. Herein we report a one and two-photon fluorescence probe (NP-C6-CXB) for COX-2, based on the conjugation of naphthalamide with Celecoxib, by using flexible hexylene linker. NP-C6-CXB is nonfluorescent in buffer solution and normal cells, while it shows bright fluorescence in solutions and cancer cells in the presence of COX-2 with an excellent selectivity. Interestingly, NP-C6-CXB can discriminate cancer cells (MCF-7) from normal cells (COS-7) in the single culture medium under confocal microscopy. Due to the selective binding affinity of NP-C6-CXB with a COX-2 enzyme, the intensity is proportional to the level of COX-2 enzyme in cancer cells. In vivo and in vitro experiments proved that NP-C6-CXB is a potential tool for identification of tumor and might be used in surgical resection of COX-2 expressed tumors.